I can’t say enough how hard it is to do what we do. I don’t say that to puff myself up&emdash;”Look at me! My job’s really hard!”&emdash;but more to dispel the notion that what we do is simple and routine. Keith Cowing takes on the premise that commercial, off-the-shelf [COTS] parts can be used in all sorts of spaceflight applications in a solid piece for SpaceRef.
Commercial carabiners are indeed strong, and can be used in rather extreme mountaineering situations where it gets rather cold. In space, however, items used during EVAs can be exposed to temperature extremes that range several hundred degrees above and below freezing in a matter of minutes – depending on whether you are in the sunlit or dark part of an orbit. As such you need to use materials that are designed to function through out these temperature ranges.
The aluminum used in commercial carabiners would likely not be practical in space given that the constant heating and freezing would likely cause deterioration in the structure of the carabiner. Indeed, carabiners used in exceptionally cold climbing frays on Earth can start to behave stiffly. It would also affect the ability of the gate to open and close – specifically the spring mechanism. While there are large carabiners that are easier to use with thick gloves, the gloves used by astronauts are not renowned for their dexterity. Having used carabiners in a variety of rock, ice, and snow situations – with gloves on – I would expect that a standard issue carabiner would be somewhat difficult to use with standard EMU gloves.
According to a NASA source who is very familiar with EVA tools design, when NASA does use off the shelf hardware, the items have to be disassembled and reworked because the majority of materials and the way in which the devices are lubricated will not survive the space environment without freezing up or becoming brittle. Socket wrenches are an example of devices that require some reworking.
We’ve run into that before.
You have to put yourself in this whole other mindest when you’re designing externally-used hardware. “What will the thermal gradient do to this assembly? How do the piece-parts expand and contract? Do we need heater mats to keep us at temperature on the cold side and multi-layer insulation to keep us cool on the warm side? Does this have any moving parts? Will the lubricants work in the thermal and zero-pressure environments?” These are questions that hardware designers have to face every day, and putting up with those requirements is generally our job in manufacturing these parts. Often times, the finishing processes take longer than the actual cutting of metal on the part.
This job is not easy. It is hard, but we do it because it is worth it. Exploration is a part of the human condition. When we do it right, it’s seen as “gee-whiz cool”, usually forgotten in a month or so [longer if it’s a manned mission, usually]. When we do it wrong, it’s never forgotten. Ours is the largest stage: all the world.